Two pressure cooker bombs at the Boston Marathon finish line killed three people and injured hundreds. In response, there were more than 27 million tweets about the bombings. People on Twitter showed solidarity for victims with the hashtag #bostonstrong.

After the former South African president's death, Twitter spiked at 95,000 tweets per minute. Madiba, Mandela's clan name, also became a trending topic on Twitter with public figures, including former president Bill Clinton, tweeting affectionately about the leader.

“Death is something inevitable.When a man has done what he considers to be his duty to his people%26his country,he can rest in peace” #Madiba